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From: Vlastimil Babka <vbabka@suse.cz>
To: Mike Kravetz <mike.kravetz@oracle.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Hillf Danton <hdanton@sina.com>, Michal Hocko <mhocko@kernel.org>,
	Mel Gorman <mgorman@suse.de>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection
Date: Mon, 5 Aug 2019 10:42:59 +0200	[thread overview]
Message-ID: <bb16d3f0-0984-be32-4346-358abad92c4c@suse.cz> (raw)
In-Reply-To: <20190802223930.30971-2-mike.kravetz@oracle.com>

On 8/3/19 12:39 AM, Mike Kravetz wrote:
> From: Hillf Danton <hdanton@sina.com>
> 
> Address the issue of should_continue_reclaim continuing true too often
> for __GFP_RETRY_MAYFAIL attempts when !nr_reclaimed and nr_scanned.
> This could happen during hugetlb page allocation causing stalls for
> minutes or hours.
> 
> We can stop reclaiming pages if compaction reports it can make a progress.
> A code reshuffle is needed to do that.

> And it has side-effects, however,
> with allocation latencies in other cases but that would come at the cost
> of potential premature reclaim which has consequences of itself.

Based on Mel's longer explanation, can we clarify the wording here? e.g.:

There might be side-effect for other high-order allocations that would
potentially benefit from more reclaim before compaction for them to be
faster and less likely to stall, but the consequences of
premature/over-reclaim are considered worse.

> We can also bail out of reclaiming pages if we know that there are not
> enough inactive lru pages left to satisfy the costly allocation.
> 
> We can give up reclaiming pages too if we see dryrun occur, with the
> certainty of plenty of inactive pages. IOW with dryrun detected, we are
> sure we have reclaimed as many pages as we could.
> 
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Hillf Danton <hdanton@sina.com>
> Tested-by: Mike Kravetz <mike.kravetz@oracle.com>
> Acked-by: Mel Gorman <mgorman@suse.de>

Acked-by: Vlastimil Babka <vbabka@suse.cz>
I will send some followup cleanup.

There should be also Mike's SOB?



> ---
>  mm/vmscan.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 47aa2158cfac..a386c5351592 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2738,18 +2738,6 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
>  			return false;
>  	}
>  
> -	/*
> -	 * If we have not reclaimed enough pages for compaction and the
> -	 * inactive lists are large enough, continue reclaiming
> -	 */
> -	pages_for_compaction = compact_gap(sc->order);
> -	inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
> -	if (get_nr_swap_pages() > 0)
> -		inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
> -	if (sc->nr_reclaimed < pages_for_compaction &&
> -			inactive_lru_pages > pages_for_compaction)
> -		return true;
> -
>  	/* If compaction would go ahead or the allocation would succeed, stop */
>  	for (z = 0; z <= sc->reclaim_idx; z++) {
>  		struct zone *zone = &pgdat->node_zones[z];
> @@ -2765,7 +2753,21 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
>  			;
>  		}
>  	}
> -	return true;
> +
> +	/*
> +	 * If we have not reclaimed enough pages for compaction and the
> +	 * inactive lists are large enough, continue reclaiming
> +	 */
> +	pages_for_compaction = compact_gap(sc->order);
> +	inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
> +	if (get_nr_swap_pages() > 0)
> +		inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);
> +
> +	return inactive_lru_pages > pages_for_compaction &&
> +		/*
> +		 * avoid dryrun with plenty of inactive pages
> +		 */
> +		nr_scanned && nr_reclaimed;
>  }
>  
>  static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
> 


  reply	other threads:[~2019-08-05  8:43 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 22:39 [PATCH 0/3] address hugetlb page allocation stalls Mike Kravetz
2019-08-02 22:39 ` [PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection Mike Kravetz
2019-08-05  8:42   ` Vlastimil Babka [this message]
2019-08-05 10:57     ` Vlastimil Babka
2019-08-05 16:58       ` Mike Kravetz
2019-08-05 18:34         ` Vlastimil Babka
2019-08-05 16:54     ` Mike Kravetz
2019-08-02 22:39 ` [PATCH 2/3] mm, compaction: raise compaction priority after it withdrawns Mike Kravetz
2019-08-05  9:14   ` Vlastimil Babka
2019-08-02 22:39 ` [PATCH 3/3] hugetlbfs: don't retry when pool page allocations start to fail Mike Kravetz
2019-08-05  9:28   ` Vlastimil Babka
2019-08-05 17:12     ` Mike Kravetz

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